The present application relates to the field of radiograph CT, and more particularly, to a CT collimator having a single motor drive system and a radiograph CT system having the CT collimator.
At present, radiograph CT systems such as X-ray CT system are widely used in various medical institutions for three-dimensional imaging of the regions of interest of the subjects to assist the clinicians to achieve an accurate medical diagnosis of the subjects.
In a radiograph CT system, a radiation tube generating cone-shaped radiation beams and a detector detecting the radiation beams rotate around a rotation center, wherein the detector is disposed opposite to the radiation tube and consists of detector elements arranged in a matrix form. Projection data generated by the radiation beams transmitting through the subject are collected; based on the collected projection data, an image of the region of interest of the subject is reconstructed; and then the reconstructed CT image is displayed on an image display device.
In a radiograph CT system, a collimator is generally provided between the radiation tube and the subject to be detected. By adjusting a width of the aperture of the collimator, the width of the radiation beams in a direction parallel to the subject is controlled so as to control a thickness of the scan.
A conventional collimator generally has at least two different motor drive systems to meet the requirements of multi-slot opening and Z-beam tracking. Such a collimator comprises at least two gates or cams, which are driven by at least two different motor drive systems, and hence have higher cost.
Some newly developed collimators use a single motor drive system to meet the requirements of slot opening and Z-beam tracking. For example, a recently developed collimator comprises a plate having a plurality of slots driven by a single motor drive system. Each slot corresponds to a collimator aperture of a different width. Though using a single motor drive system in place of the conventional two drive systems to reduce the cost of the drive system, such a collimator requires converting the rotational motion of the motor into a linear motion and hence the need of such components as lead screw and rails. Therefore, there is a need for a CT collimator and a CT system that, in case of a focus shift of the radiation source due to temperature changes during a CT scan, can automatically correct the position of the collimator aperture and enable the radiation beams to be irradiated to the subject via the collimator directly in a rotational movement manner without departing from the predetermined region of interest so that the detection area of the radiation beams projected to the detector after passing through the subject remains unchanged.